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Upgraded Indestructible LED Lanterns 



Make] Projects 



Upgraded Indestructible LED 
Lanterns 

Written By: jduffyl05 



TOOLS: 


PARTS: 


Electrical Taped) 


555 timer (cmos or normal) (1) 


PVC cement & applicator (1) 


1/4W 470 ohm resistor (2) 


Solder (I recommend 0.032" solder, as 


handful of 2n3906 transistors (exact 


you can get a pound for $10 from 


number varies depending on primary 


Radioshack) (1) 


coil) (1) 


Solderina iron (1) 


0.01 uf capacitor (103) (2) 


Wire cutter/stripper (1) 


PC board (1) 


drill and/or reamer (1) 


mylar capacitor (any value above 0.005) 




01 




indicator LEDs (different colors) (2) 




rechargable AA battery (1) 




sinale AA battery holder (1) 




high brightness white led (1) 




1/4W 1k ohm resistor (1) 




1/4W 2.2k ohm resistor (1) 




4401. 2222. or 3904 transistor (1) 



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Pagel of 6 



Upgraded Indestructible LED Lanterns 



inductor (see step 2) (1) 



SUMMARY 

The original LED lanterns were featured in MAKE: Magazine, issue 30. When I first saw the 
article, I thought that they could only be used once, as they would have to be glued shut. 
When I read it, I realized that they were sealed with tape, and could therefore be opened, but 
not before I came up with a new idea. 



Step 1 — Upgraded Indestructible LED Lanterns 




• The first step is to build the charger. 

• This is a basic 555 oscillator, with a frequency of about 160KHz. 

• You MUST hook up several 3906s in parallel, or it will fry quickly. Apply 12V, and 10 
transistors, then remove one transistor at a time until the remaining ones are too hot to 
touch. Replace ALL transistors with new ones, plus the removed one. It should run 
continuously without overheating. 

• L1 is a wire coil of about 20-25 turns of magnet wire. It should have a diameter about that 
of the inside of the PVC cap. 

• This should be powered by large, rechargable batteries or a power supply at about 9V. A 
9V battery will run out of power quickly, and will not deliver enough current. 

• If you have a CMOS 555, you should be able to increase the frequency by replacing the 
2.2K resistor with a 470ohm resistor, and the 0.01 uf cap with a 0.0047 cap. This should 
increase the inductive reactance of the coil, and allow you to use fewer transistors. 



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Page 2 of 6 



Upgraded Indestructible LED Lanterns 



Step 2 




• Now, we build the LED driver and battry charger circuit. Note that this will have to fit inside 
a 3" piece of 1" diameter PVC. The coil also must fit in a 1" endcap. It should be 20-25 
turns air core (2nd picture). 

• If this looks familiar, it is because it is a joule thief with a wireless power receiver. The coil 
labeled "coil (see step 2)" is made by wrapping 2 wires around a doughnut-shaped ferrite 
core six or seven times. The top two and bottom two wires are the same, so you connect 
one end of one wire to the other end of the other wire. 

• If you turn on the sender from step 1 and place the receiver coil flat on top of the sender 
coil, the indicator LEDs should light up. Charge the battery in its normal charger. When put 
into the circuit, the white LED should light. When the receiver coil is put near the sender, 
the indicators should light, and the white LED should turn off. If the white LED stays lit, flip 
the receiver coil. Make sure to mark which side works, as this is very important. 

• If the white LED does not light, check your wiring. If rechecking does not work, watch Bre 
Pettis's video on the joule thief, as he does a better job explaining the joule thief part of the 
circuit. 



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Page 3 of 6 



Upgraded Indestructible LED Lanterns 



Step 3 




• If everything works, completely 
drain your battery by using a 
resistor. DO NOT CONNECT THE 
ENDS DIRECTLY, you must use at 
least a 15 ohm resistor. Once it is 
drained, put it into the receiver 
circuit. None of the LEDs should 
light. 

• Now, place the receiver coil on the 
sender coil as in step 2. 

• The indicators should light up, and 
after about 15 minutes, removing 
the power to the sender or moving 
the coils apart should turn off the 
indicators, and turn on the white 
LED. 

• If it does, then everything is 
working. If not, check wiring, coil 
polarity, the sender, and the 
battery. 



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Page 4 of 6 



Upgraded Indestructible LED Lanterns 



Step 4 




• Now, drill a hole in one PVC cap 
the size of your LED. 

• Put a bead of waterproof glue 
around the base of the LED, and 
insert it into the hole, with the rest 
of the circuit attached. Fit the 
indicator LEDs just behind the 
white LED, so that when they are 
on, you can see the light through 
the white LED, as in the picture. 

• Slide the 3" piece of 1" PVC over 
the circuit and the battery into the 
cap. 

• Test-fit the coil at the bottom of the 
undrilled cap, and slide it onto the 
PVC tube. 

• Test it with the sender circuit, 
placing the sender coil just outside 
the PVC cap. 

• As before, the white LED should 
turn off, and the indicator LEDs 
should turn on. if you did it 
correctly, the light from them 
should be visible through the top of 
the white LED (as in photo). 



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Page 5 of 6 



Upgraded Indestructible LED Lanterns 



Step 5 




• If everything works, then hot-glue the coil in place, and tape, glue, or epoxy the circuit and 
battery in place. 

• Then, pull the cap with the LED off, turn it 1/4 turn in one direction, and apply PVC glue to 
the pipe where the cap will slip on. The circuit will probably get in the way of the cap, so 
only glue the tube. 

• Then slide the cap on, and turn it 1/4 back to its original position. Test the circuit one last 
time. If you want it to be almost totally indestructable, then fill the pipe with epoxy before 
adding the second cap. If you are doing this, glue the cap with the LED first, as the cap 
with the coil does not protrude as far into the pipe. 

• Finish by gluing the second cap onto the pipe in the same way as the first. 

• Test it once again 

• You're done! 



st generated on 2012-11-01 07:40:37 AM. 



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Page 6 of 6